首先，不要一步登天直接解決多人聊天這個問題，先把問題化簡。
1.多人聊天的核心問題是服務器如何標識不同的客戶端，如何根據客戶端的需求轉發消息給指定客戶端。
2.多人聊天轉化為C-C聊天，但是不再是直接C-C，而是通過server轉發消息，所以變成==>C-S-C。
3.server如何允許2個client同時連接，設置listen函數的第二個參數，最大連接數。
4.server如何標識兩個client，用一個結構體數組來存放兩個client的信息。
5.server如何轉發消息給client，很簡單，先接收到的發送給還沒接收到的。如圖：
6.server如何管理兩個client的連接狀態，連接成功很簡單，就是accpet成功后就是連接成功了。但是怎么判斷連接斷開呢？這個涉及到的select函數的使用，有點復雜~，所以我就簡單的用了一個send函數發送一個空消息來判斷是否斷開連接，這個不嚴謹，容易出BUG，但是實踐起來簡單就使用了它。
7.要用線程來管理接收消息、發送消息、接受請求、管理連接狀態。
技術要點：C語言線程函數的使用。
_beginthreadex函數原型_ACRTIMP uintptr_t __cdecl _beginthreadex( _In_opt_ void* _Security,//安全屬性，NULL為默認安全屬性 _In_ unsigned _StackSize,//線程堆棧的大小。如果為0，則線程堆棧大小和創建它的線程的相同。一般用0 _In_ _beginthreadex_proc_type _StartAddress, //線程函數的地址 _In_opt_ void* _ArgList, //傳進線程的函數 _In_ unsigned _InitFlag, //線程初始狀態，0:立即運行；CREATE_SUSPEND：懸掛（如果出事狀態定義為懸掛，就要調用ResumeThread(HANDLE) 來激活線程的運行） _Out_opt_ unsigned* _ThrdAddr //用于記錄線程ID的地址 )
例子:
#include <process.h>#include <stdio.h>unsigned __stdcall Thread(void* param){ printf("%d/n", *(int*)param); //這里必須先要強行轉換為int*，不然void* 直接解引用會出錯。 return 0;}int main(){ int i = 0; _beginthreadex(NULL, 0, Thread, &i, 0, NULL); return 0;}1V1,C-S-C聊天例子：
編寫環境：win10，VS2015
效果圖：
server code：
#include <WinSock2.h>#include <process.h>#include <stdio.h>#include <stdlib.h>#pragma comment(lib,"ws2_32.lib")#define SEND_OVER 1 //已經轉發消息#define SEND_YET 0 //還沒轉發消息int g_iStatus = SEND_YET;SOCKET g_ServerSocket = INVALID_SOCKET; //服務端套接字SOCKADDR_IN g_ClientAddr = { 0 }; //客戶端地址int g_iClientAddrLen = sizeof(g_ClientAddr);bool g_bCheckConnect = false; //檢查連接情況HANDLE g_hRecv1 = NULL;HANDLE g_hRecv2 = NULL;//客戶端信息結構體typedef struct _Client{ SOCKET sClient; //客戶端套接字 char buf[128]; //數據緩沖區 char userName[16]; //客戶端用戶名 char IP[20]; //客戶端IP UINT_PTR flag; //標記客戶端，用來區分不同的客戶端}Client;Client g_Client[2] = { 0 }; //創建一個客戶端結構體//發送數據線程unsigned __stdcall ThreadSend(void* param){ int ret = 0; int flag = *(int*)param; SOCKET client = INVALID_SOCKET; //創建一個臨時套接字來存放要轉發的客戶端套接字 char temp[128] = { 0 }; //創建一個臨時的數據緩沖區，用來存放接收到的數據 memcpy(temp, g_Client[!flag].buf, sizeof(temp)); sprintf(g_Client[flag].buf, "%s: %s", g_Client[!flag].userName, temp);//添加一個用戶名頭 if (strlen(temp) != 0 && g_iStatus == SEND_YET) //如果數據不為空且還沒轉發則轉發 ret = send(g_Client[flag].sClient, g_Client[flag].buf, sizeof(g_Client[flag].buf), 0); if (ret == SOCKET_ERROR) return 1; g_iStatus = SEND_OVER; //轉發成功后設置狀態為已轉發 return 0;}//接受數據unsigned __stdcall ThreadRecv(void* param){ SOCKET client = INVALID_SOCKET; int flag = 0; if (*(int*)param == g_Client[0].flag) //判斷是哪個客戶端發來的消息 { client = g_Client[0].sClient; flag = 0; } else if (*(int*)param == g_Client[1].flag) { client = g_Client[1].sClient; flag = 1; } char temp[128] = { 0 }; //臨時數據緩沖區 while (1) { memset(temp, 0, sizeof(temp)); int ret = recv(client, temp, sizeof(temp), 0); //接收數據 if (ret == SOCKET_ERROR) continue; g_iStatus = SEND_YET; //設置轉發狀態為未轉發 flag = client == g_Client[0].sClient ? 1 : 0; //這個要設置，否則會出現自己給自己發消息的BUG memcpy(g_Client[!flag].buf, temp, sizeof(g_Client[!flag].buf)); _beginthreadex(NULL, 0, ThreadSend, &flag, 0, NULL); //開啟一個轉發線程,flag標記著要轉發給哪個客戶端 //這里也可能是導致CPU使用率上升的原因。 } return 0;}//管理連接unsigned __stdcall ThreadManager(void* param){ while (1) { if (send(g_Client[0].sClient, "", sizeof(""), 0) == SOCKET_ERROR) { if (g_Client[0].sClient != 0) { CloseHandle(g_hRecv1); //這里關閉了線程句柄，但是測試結果斷開連C/S接后CPU仍然瘋漲 CloseHandle(g_hRecv2); printf("Disconnect from IP: %s,UserName: %s/n", g_Client[0].IP, g_Client[0].userName); closesocket(g_Client[0].sClient); //這里簡單的判斷：若發送消息失敗，則認為連接中斷(其原因有多種)，關閉該套接字 g_Client[0] = { 0 }; } } if (send(g_Client[1].sClient, "", sizeof(""), 0) == SOCKET_ERROR) { if (g_Client[1].sClient != 0) { CloseHandle(g_hRecv1); CloseHandle(g_hRecv2); printf("Disconnect from IP: %s,UserName: %s/n", g_Client[1].IP, g_Client[1].userName); closesocket(g_Client[1].sClient); g_Client[1] = { 0 }; } } Sleep(2000); //2s檢查一次 } return 0;}//接受請求unsigned __stdcall ThreadAccept(void* param){ int i = 0; int temp1 = 0, temp2 = 0; _beginthreadex(NULL, 0, ThreadManager, NULL, 0, NULL); while (1) { while (i < 2) { if (g_Client[i].flag != 0) { ++i; continue; } //如果有客戶端申請連接就接受連接 if ((g_Client[i].sClient = accept(g_ServerSocket, (SOCKADDR*)&g_ClientAddr, &g_iClientAddrLen)) == INVALID_SOCKET) { printf("accept failed with error code: %d/n", WSAGetLastError()); closesocket(g_ServerSocket); WSACleanup(); return -1; } recv(g_Client[i].sClient, g_Client[i].userName, sizeof(g_Client[i].userName), 0); //接收用戶名 printf("Successfuuly got a connection from IP:%s ,Port: %d,UerName: %s/n", inet_ntoa(g_ClientAddr.sin_addr), htons(g_ClientAddr.sin_port), g_Client[i].userName); memcpy(g_Client[i].IP, inet_ntoa(g_ClientAddr.sin_addr), sizeof(g_Client[i].IP)); //記錄客戶端IP g_Client[i].flag = g_Client[i].sClient; //不同的socke有不同UINT_PTR類型的數字來標識 i++; } i = 0; if (g_Client[0].flag != 0 && g_Client[1].flag != 0) //當兩個用戶都連接上服務器后才進行消息轉發 { if (g_Client[0].flag != temp1) //每次斷開一個連接后再次連上會新開一個線程，導致cpu使用率上升,所以要關掉舊的 { if (g_hRecv1) //這里關閉了線程句柄，但是測試結果斷開連C/S接后CPU仍然瘋漲 CloseHandle(g_hRecv1); g_hRecv1 = (HANDLE)_beginthreadex(NULL, 0, ThreadRecv, &g_Client[0].flag, 0, NULL); //開啟2個接收消息的線程 } if (g_Client[1].flag != temp2) { if (g_hRecv2) CloseHandle(g_hRecv2); g_hRecv2 = (HANDLE)_beginthreadex(NULL, 0, ThreadRecv, &g_Client[1].flag, 0, NULL); } } temp1 = g_Client[0].flag; //防止ThreadRecv線程多次開啟 temp2 = g_Client[1].flag; Sleep(3000); } return 0;}//啟動服務器int StartServer(){ //存放套接字信息的結構 WSADATA wsaData = { 0 }; SOCKADDR_IN ServerAddr = { 0 }; //服務端地址 USHORT uPort = 18000; //服務器監聽端口 //初始化套接字 if (WSAStartup(MAKEWORD(2, 2), &wsaData)) { printf("WSAStartup failed with error code: %d/n", WSAGetLastError()); return -1; } //判斷版本 if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) { printf("wVersion was not 2.2/n"); return -1; } //創建套接字 g_ServerSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); if (g_ServerSocket == INVALID_SOCKET) { printf("socket failed with error code: %d/n", WSAGetLastError()); return -1; } //設置服務器地址 ServerAddr.sin_family = AF_INET;//連接方式 ServerAddr.sin_port = htons(uPort);//服務器監聽端口 ServerAddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);//任何客戶端都能連接這個服務器 //綁定服務器 if (SOCKET_ERROR == bind(g_ServerSocket, (SOCKADDR*)&ServerAddr, sizeof(ServerAddr))) { printf("bind failed with error code: %d/n", WSAGetLastError()); closesocket(g_ServerSocket); return -1; } //設置監聽客戶端連接數 if (SOCKET_ERROR == listen(g_ServerSocket, 20000)) { printf("listen failed with error code: %d/n", WSAGetLastError()); closesocket(g_ServerSocket); WSACleanup(); return -1; } _beginthreadex(NULL, 0, ThreadAccept, NULL, 0, 0); for (int k = 0;k < 100;k++) //讓主線程休眠，不讓它關閉TCP連接. Sleep(10000000); //關閉套接字 for (int j = 0;j < 2;j++) { if (g_Client[j].sClient != INVALID_SOCKET) closesocket(g_Client[j].sClient); } closesocket(g_ServerSocket); WSACleanup(); return 0;}int main(){ StartServer(); //啟動服務器 return 0;}client code:
#define _WINSOCK_DEPRECATED_NO_WARNINGS#include <WinSock2.h>#include <process.h>#include <stdio.h>#include <stdlib.h>#include <conio.h>#pragma comment(lib,"ws2_32.lib")#define RECV_OVER 1#define RECV_YET 0char userName[16] = { 0 };int iStatus = RECV_YET;//接受數據unsigned __stdcall ThreadRecv(void* param){ char buf[128] = { 0 }; while (1) { int ret = recv(*(SOCKET*)param, buf, sizeof(buf), 0); if (ret == SOCKET_ERROR) { Sleep(500); continue; } if (strlen(buf) != 0) { printf("%s/n", buf); iStatus = RECV_OVER; } else Sleep(100); } return 0;}//發送數據unsigned __stdcall ThreadSend(void* param){ char buf[128] = { 0 }; int ret = 0; while (1) { int c = getch(); if(c == 72 || c == 0 || c == 68)//為了顯示美觀，加一個無回顯的讀取字符函數 continue; //getch返回值我是經過實驗得出如果是返回這幾個值，則getch就會自動跳過，具體我也不懂。 printf("%s: ", userName); gets_s(buf); ret = send(*(SOCKET*)param, buf, sizeof(buf), 0); if (ret == SOCKET_ERROR) return 1; } return 0;}//連接服務器int ConnectServer(){ WSADATA wsaData = { 0 };//存放套接字信息 SOCKET ClientSocket = INVALID_SOCKET;//客戶端套接字 SOCKADDR_IN ServerAddr = { 0 };//服務端地址 USHORT uPort = 18000;//服務端端口 //初始化套接字 if (WSAStartup(MAKEWORD(2, 2), &wsaData)) { printf("WSAStartup failed with error code: %d/n", WSAGetLastError()); return -1; } //判斷套接字版本 if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) { printf("wVersion was not 2.2/n"); return -1; } //創建套接字 ClientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); if (ClientSocket == INVALID_SOCKET) { printf("socket failed with error code: %d/n", WSAGetLastError()); return -1; } //輸入服務器IP printf("Please input server IP:"); char IP[32] = { 0 }; gets_s(IP); //設置服務器地址 ServerAddr.sin_family = AF_INET; ServerAddr.sin_port = htons(uPort);//服務器端口 ServerAddr.sin_addr.S_un.S_addr = inet_addr(IP);//服務器地址 printf("connecting....../n"); //連接服務器 if (SOCKET_ERROR == connect(ClientSocket, (SOCKADDR*)&ServerAddr, sizeof(ServerAddr))) { printf("connect failed with error code: %d/n", WSAGetLastError()); closesocket(ClientSocket); WSACleanup(); return -1; } printf("Connecting server successfully IP:%s Port:%d/n", IP, htons(ServerAddr.sin_port)); printf("Please input your UserName: "); gets_s(userName); send(ClientSocket, userName, sizeof(userName), 0); printf("/n/n"); _beginthreadex(NULL, 0, ThreadRecv, &ClientSocket, 0, NULL); //啟動接收和發送消息線程 _beginthreadex(NULL, 0, ThreadSend, &ClientSocket, 0, NULL); for (int k = 0;k < 1000;k++) Sleep(10000000); closesocket(ClientSocket); WSACleanup(); return 0;}int main(){ ConnectServer(); //連接服務器 return 0;}這程序還有一些BUG，其中最大的就是關掉一個連接后CPU使用率瘋漲，我測試過我想到的可能，還是找不到結果~，希望有大神懂的告知一下。
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網。
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